1. Field of the Invention
The present invention relates generally to wireless communications. In particular, the present invention relates to a Push-To-Talk (PTT) service method for allowing a PTT group call to be recorded for play back.
2. Description of the Related Art
Typically, a radio communication system comprising portable terminals divides a total service area into a plurality of smaller cell areas covered by base stations (BSs), and the BSs are under the centralized control of mobile switching centers (MSCs) to enable subscribers to call and maintain a call, while roaming across different cells.
Due to the development of communication technology, many techniques for integrating an Internet Protocol (IP) network with a wireless communication network have been developed. One such technique is Voice over IP (VoIP), a packet-based voice service using IP.
Traditionally, the VoIP service sets up a call via a mobile communication network and an IP network, which takes a long time. This shortcoming can be overcome by an interactive call service, such as a group call and a private call, relying on the multicast functionality of the IP network. An interactive call is a call made with user interactions. An example of the interactive call is a walkie-talkie type PTT call. A group call is a multi-user call which a plurality of PTT users initiate or participate in, simultaneously. A private call is a one-to-one call within a distinct group.
The PTT service enables simultaneous voice/data service for a plurality of users or in a group. A PTT user presses a PTT button to speak and the user's PTT-enabled portable terminal (hereinafter, referred to as a PTT portable terminal) transmits a PTT service request to a network. The network rejects the request or allocates required resources for the PTT call based on a predetermined criterion such as the availability of resources or the priority level of the user. At the same time, connections are established between the PTT user and all other active users within a predetermined subscriber group. After the voice connection is established, the PTT user can speak and the other users can hear on the channel. When the PTT user releases the PTT service, the PTT portable terminal transmits a release message to the network and the resources are released. This PTT communication system enables one-to-one and one-to-many or multi-party communications. The one-to-many communication is called a PTT group call in the PTT service.
A PTT call is initiated as a calling PTT portable terminal requests the PTT call to a receiving PTT portable terminal. The PTT call request is issued by pressing a PTT button. The receiving PTT portable terminal notifies the called party that the caller wants to talk to the called party on the PTT call (Talk Indication). The called party speaks with the caller during the PTT call.
With this conventional PTT service, however, a PTT user has no way of determining what was discussed at a PTT group call if the PTT user dropped the PTT group call during the call.
For example, if a PTT group call is made about a travel plan and one of the group members quits the call to turn to something urgent before the call ends, after the call has ended the user has no way of determining what was discussed during the user's absence.
Therefore, the user must call up other parties to ask what was discussed in the call during the user's absence. However, the user may not be provided with every detail of the conversation that took place among the group call members during the call.